Pull head for broaching machines



Aug- 20, 1946- I F. J. LAPOINTE 2,405,961

PULL HEAD FOR BROACHING MACHINESl Filed Dec. 18, 1943 INVEN TOR.

Wg@ .fg/'manie Patented Aug. 20,1946

PULL HEAD FOR BROACHING MACHINES Francis J. Lapointe, Ann Arbor, Mich., assignor to American Broach & Machine Co., Ann Arbor, Mich., a corporation of Michigan Application December 18, 1943, Serial No. 514,733

Claims. (Cl. 279-79) This invention relates to breaching machines and is concerned with the pull head of such a machine in which the shank of the broach is rcmovably secured. It is customary to make the smaller broaches with a round shank having a transversely extending notch, usually arcuate in cross section, and to provide a pull head with a bore to receive the shank and a cross bore intersecting it in position to register with the notch so that a locking Din may be inserted for holdingV the broach in the pull head. Thisarrangement, however, is not entirely satisfactory, in that it requires the notch in the broach shank to be carefully registered with the cross bore before the pin can be inserted, and also requires extreme accuracy in the construction of all of the parts to insure that they shall fit properly.

One object of the present invention is to provide a new and improved pull head designed to receive this type of broach shank, and provided with locking mechanism which shall be substantially automatic in its engagement with the broach and which shall be readily disengageable therefrom.

Another object of the invention is to provide a pull head having a locking member to cooperate with a notch in the broach shank and yielding means urging the locking member into position for such engagement and permitting it to be forced aside as the broach shank is entered in the pull head.

A further object of the invention is to provide a pull head having a locking member designed to engage a notch in a broach shank and movable along a path oblique to the axis of the shank so arranged that the working strain on the broach tends to tighten the locking member in its engagement.

It is also an object of the invention to provide a pull head with a spring-pressed locking member for engaging a broach shank and with means externally accessible on the pull head for releasing the locking member at will or automatically at the end of the stroke of the broaching machine.

Other objects and advantages of the invention will appear from the following description taken in connection with the drawing in which:

Fig. 1 is a side elevation showing a pull head embodying this invention, with a broach inserted therein.

Fig. 2 isa vertical section of the pull head taken on a larger scale and showing the locking member engaged with the shank portion of a broach.

Fig. 3 is a transverse vsection taken as indicated at the line 3-3 on Fig. 2.

Fig. 4 is a vertical sectional view similar to Fig.

2, but showing` the locking member retracted to release position and the broach shank removed from the bore of the tool head.

While there is illustrated in the drawing and hereinafter described, a preferred form of the invention, it is contemplated that various modifications may be made by those skilled in the art without departing from the spirit and scope of the appended claims.

As shown in the drawing, the pull head is formed from a solid block of metal providing a body portion I of rectangular cross section and a shank 2 which is threaded at 3 for securement in the cross head of a broaching machine indicated in dotted outline at 4. A circular lock nut 5 is shown on the threaded shank 3 in accordance with standard construction,

The block I is: provided with a bore 6 dimensioned to receive the shank 'I of a broach 8, and, as shown in Figs. 2 and 4, this shank 'l is formed with a transverse notch 9 which is preferably arcuate in cross section. The locking member of the tool head is round in cross section and of such a radius that it will t in the arcuate notch or groove 9 of the shank 1. In the construction shown this round locking member is a cylindrical pin I0 which is carried in a guideway II eXtendf ing obliquely in the block I with respect to the axis of the bore 6. This guideway is in the form of a slot cut transversely through the block I and opening through both side walls thereof, and, as shown in Fig. 3, the end portions I (la of the pin I0 project beyond the side Walls so as to be externally accessible for moving. the pin manually, if desired. The pin is held in place Iby a pair of snap rings I2, I2 tted into grooves in the pin adjacent the side walls of the block I, as shown in Fig. 3. The guideway II provides a path for movement of the locking member Ill into and out of locking position, this path extending divergently with respect to the inner end of the bore 6 so that when the pin is pushed inwardly along the path it is automatically carried out of the bore 6. Spring means is provided for holding the pin normally in its locking position, but whether such means is included in the construction, or gravity is relied upon` to carry the pin to locking position, it will be easily forced back along the divergent guideway I I when the end of the shank 'I is entered in the bore S, and this action is somewhat facilitated by reason of the fact that the locking member I0 is circular in cross section so that it can either slide or roll along the slot II when pressure is applied in the direction of the axis of the bore 6 by the entry of the shank 'I therein.

The spring means for controlling the locking member I comprises a coil spring I3 and a plunger I4 which is slidably mounted in a bore I extending parallel to the bore B in the block I. The plunger is formed with a notch IE which embraces the locking pin IB, as seen in Figs. 2 and 4, and the spring I3 is pocketed in the inner end of the bore I-5 so as to urge the plunger I4 outwardly and thus carry the pin It) toward its locking position, in which it will engage in the notch 9 of the broach shank 'I. When the bore 6 is empty, the spring-pressed movement of the locking member l0 is arrestedby encounter of the pin I0 with the lower end Ha of the guide slot I I; but in locking engagement with the notch 9 the pin I0 may not reach this end surface I Ia of the slot I I, since it will tend to be. wedged 'between the inclined top wall IIb of the slot II and the surface of the notch Siv in the shank 'I. Preferably, the pin will stop just short of the end of the slot so as to insure its rm engagement in the notch 9 of the broach shank. Then, during the working stroke, a pull on the broach will tend to wedge the pin I Il more tightly between the wall of the notch 9 and the inclined wall IIb of the guide slot and will press the opposite side of the broach shank 'l rmly against the boreY 6, thus holding it positively and steadily in working position in the pull head.

When it is desired to remove the broach from the pull head the operator will place his thumb and first finger against opposite end portions IIJa of the locking pin Ill and push the pin upwardly along the inclined guideway I I out of engagement with the notch 9, so that he can grasp the broach shank with his other hand 'and withdraw'it from the pull head. In some operations it is desirable to have this release eiected automatically, and for that purpose the plunger'Ill is equipped with a tappet screw I I threaded into its outer end and provided with a lock nut I8 so that the screw can be adjusted to engage a part of the broaching machine at the proper instant in the return stroke of the pull head and thus release the broach to permit its insertion in a new work-piece.

With the construction shown it is a comparatively sirnple matter for the operator to insert the broach in the pull head, becauseeven though the shank '1. is inserted with the notch 9 turned away from the locking pin I0, the operator can easily rotate the shank in the bore 6 until the notch 9 is brought into position to receive the pin I Il, the latter being spring-pressed to its locking position and thus entering the notch automatically when theparts are so registered.

I claim as my invention:

1. A pull head to receive a broach shank in which there is a transverse notch of arcuate cross section, said head having a bore to iit the shank, a slot extending transversely'through the head and obliquely with respect to the axis of said bore, said slot intersecting the bore at the portion thereof which is occupied by the notch of the broach shank when said shank is inserted in working position therein and extending from said intersection divergently with respect to the inner end portion of the bore, a round locking pin in said slot dimensioned to nt the notch in the shank and movable in the slot into said intersecting portion thereof for such engagement, the-ends of said pin projecting from said slot beyond the side walls of the pull head, a second bore in the pull head parallel to the iirst'with a plunger slidable in said second bore and formed with a notch in which said locking pin is captive,

together with a spring pocketed in the second bore and reacting against the plunger to urge the pin yieldingly into position for engaging the notch in the broach shank.

2. A pull head to receive a broach shank in which there is a transverse notch of arcuate cross section, said head having a bore to t the shank, a slot extending transversely through the head and obliquely with respect to the axis of said bore, said slot intersecting the bore at the portion thereof which is occupied by the notch of the broach shank when said shank is inserted in working position therein and extending from said intersection divergently with respect to the inner end portion of the bore, a round locking pin in said slot dimensioned to t the notch in the shank and movable in the slot into said intersecting portion thereof for such engagement, a second boreA in the pull head parallel to the first with a plunger slidable in said second bore and formed with a notch in which said locking pin is captive, together with a spring pocketed in the second bore and reacting against the plunger to normally move the plunger outwardly and'urge the pin yieldingly into position for engaging the notch and in said broach shank. i

3. A pull head to receive a broach shank in which there is a transverse notch of arcuate cross section, said head having a bore to t the shank, a slot extending transversely through the head and obliquely withf respect to the axis of said bore, said slot intersecting the bore at the portion thereof which is occupied by the notch of the broach shank when said shank is inserted in working position therein and extending from said intersection divergently with respect to the inner end portion of the bore, a round locking pin in said slot dimensioned to fit the notch in the shank and movable in theslot into said intersecting portion thereof for vsuch engagement, and a second bore in the pull head parallel to the'rst with a plunger slidable in said second bore and formed with a notch in which said locking pin is captive.

4. A pull head to receive a broach shank in which there is a transverse notch of arcuate cross section, said head having a bore to nt theV shank, a slot extending transversely in the head and obliquely with respect-to the axis of saidl bore, said slot intersecting the bore at the portion thereof which is occupied by the notch of the broach shank when said shank is inserted in working position therein and extending from said intersection divergently with respect to the inner end of the bore, a round locking pin in said slot dimensioned to t the notch inthe shank and movable in the slot into said intersecting portion thereof for such engagement, and a second bore in the pull head parallel to the first with a plunger slidable vin said second bore and formed with' a transversely extending notch, the width of said last mentioned notch being substantially equalA to the diameter of said pin and said slot opening through the pull head at one side thereof whereby the pin may be inserted through the open end of the slot and engaged in the notch of the plunger becoming captive therein and being movable along the oblique slot by axial movement ofthe plunger in said second bore, said pin comprising the sole means retaining the plunger in said second bore.

5. A pull head to receive a broachshank in which there is a transverse notch, said head having a bore to slidably receive the shank; a slot extending transversely in the'head and obliquely with respect to the axis of the-bore, said slot intersecting the bore at the portion thereof which is occupied by the notch of the breach shank when said shank is inserted in Working position therein, said slot extending divergently from said intersection with respect to the inner end of the bore, a locking pin in said slot dimensioned to be seated in the notch in the shank and movable in the slot into said intersecting portion thereof for such engagement, a second bore in the pull head parallel to the first, a plunger slidable in Said second bore and formed with a transversely extending notch, the width of the last mentioned notch 10 and oblique movement of the locking pin in the divergent slot.

FRANCIS J. LAPOINTE. 

